Knock detector for internal-combustion engines



1929. R. J. LAWRENCE 1,725,872

KNOCK DETECTOR FOR INTERNAL COMBUSTION ENGINES I Filed May 1, 1928 noantoz ROLL/11m J LAWRENCE Patented .Aug. 27, 1929.

NYE-TED, STATES 1,725,872 PATENT OFFICE.

HOLLAND J. LAWRENCE, OF CHICAGO, ILLINOIS, ASSIGNOR TO PURE OIL COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION 01 OHIO.

Application filed May 1, 1928. Serial No. 274,295.

This ihvention relates to improvements in devices by means of which an audible determination may be made regarding the character of the knock produced by the combustion of fuel in the cylinders of internal combustion engines, and has for its primary ob? ject the provision of means for facilitating detonation tests on difi'erentkinds of fuels which are used for operating internal combustion engines.

Motor fuels differ widely with .respect to their combustion properties. Some of such fuels burn very rapidly when under compression of a character similar to that produced in internal combustion engines operations, with the result that inhigh compression engines such rapid burning fuels cannot be used successfully because of the resulting detonation or vibration which they impart to the engine in which they are used. Many fuels have been recently developed for internal combustion engines wherein the rate of combustion is appreciably slower, such for example as gasoline blended with benzol to the extent of 60 parts of gasoline with parts of benzol, or other hydrocarbon of the aromatic series. Again, cracking processes for producing motor fuels have been produced which provide condensate which without blending present the high anti-knock value and in other systems a mixture of ordinary gasoline with tetra-ethyl-lead are utilized which produce a motor fuel capable of resisting detonation in automobile engines. 1 It is, therefore, an object ofthe present invention to provide a simple, economical and readily operated appliance by means of which an investigator using an audible system of testing may determine quickly and satisfactorily the anti-knock value of any given fuel and the-class of such in the cylinders of an internal combustion engine, whereby the relative anti-knock value of such a fuel may be quickly determined without resort to the more delicate, expensive and complicated. devices hitherto utilized for securing equivalent results.

' For a further understanding of the invention reference is to be had to the following description and to theaccompanying drawings, wherein there has been illustrated diagrammatically the apparatus utilized in carrying out the preferred mode of operation of the invention.

Connected with the outer end of the bolt member is a taut wire 3, which comprises a stylus, and is employed to transmit the vibra tions developed in the engine to an ordina telephone transmitter 4;. The wire 3 is pre erably provided at points along its length with rubber sleeves 5 for the purpose of eliminating metallic interference. The up or or outer end of the wire, removed from t e engine head, is connected with the frame 6 of the transmitter 4, so that the vibrations de veloped in the engine, as the result of the combustion of the particular fuel used, may be directly imparted to the transmitter. To maintain the wire 3 in a taut or tight condition, necessary for the efiective operation, there is connecteol'with said wire a spring 7, which automatically maintains said wire or stylus under tension of a requisite character,

Leading from the transmitter 4 are wires 8, which extend to a sourceof electrical energy 9 and also to a multi-stage audion amplifier 10. From the output of this amplifier wires 11 lead to a set of headphones 12 or other type] of receiver or reproducer. For ordinary testing purposes, however, I prefer to use the headphones.

In operation, the vibrations resulting from fuel combustion and detonation within the engine cylinders, are transmitted by way of the taut stylus to the telephone transmitter 4. These mechanical vibrations are then translated into electrical energy by the transmitter and through the.provision of the au- The use of this system or apparatus enables I i an investigator to readily determine the char acter of the motor, fuel under test in so far as its detonating properties are'concerned and permits of a more accurate determination of the anti-knock pro erties of a motor fuel than can be secured by t e so-called bouncing pin method of knock determination. It will be understood that the invention is not limited to the details of construction and arrangement herein specifically described but that the system is subject to such modifications that may be said to fall fairly within the scope of the following claims.

What is claimed is: 1. In apparatus for detecting fuel detonation in internal combustion engines, a plug adapted to be connected with the head of an internal combustion engine, a telephone transmitter, a cable tautly stretched between said plug and said telephone transmitter, an electrical circuit in which said transmitter is situated, an audion amplifier for increasing the signal strength of the electrical oscillations developed in said circuit in response to the mechanical motion imparted to the transmitter by said cable, and a knock detector in the output circuit of said amplifier.

2. In apparatus for determining fuel detoand the head of an engine under test, said element serving to mechanically operate said transmitter to produce fluctuating oscillations in an electrical circuit connected therewith, such oscillations being proportion to the vibratory motion of the tautlymaintained element, an audion amplifier arranged in the circuit with said transmitter for augmenting the strength of such electrical: oscillations, and an audible detector disposed in the output circuit of said amplifier.

In testimony whereof I afix my signature.

HOLLAND J. LAWRENCE. 

